shared-models

Shared Models for KMP

Design and implement data models that work across all platforms in shared/commonMain.

Core Dependencies

// build.gradle.kts (shared module)
kotlin {
    sourceSets {
        commonMain.dependencies {
            implementation("org.jetbrains.kotlinx:kotlinx-serialization-json:1.11.0")
            implementation("org.jetbrains.kotlinx:kotlinx-datetime:0.8.0")
            // As of kotlinx-datetime 0.7, Instant/Clock moved to kotlin.time
            // (import kotlin.time.Instant / kotlin.time.Clock); LocalDate/TimeZone stay in kotlinx.datetime.
            // 0.7.1+ keeps kotlinx.datetime.Instant/Clock as typealiases for migration.
            // kotlin.time.Instant/Clock are stable since Kotlin 2.3; on 2.1.20-2.2.x they still
            // require @OptIn(ExperimentalTime::class).
        }
    }
}

Enable serialization plugin:

plugins {
    kotlin("multiplatform") version "2.4.10"
    kotlin("plugin.serialization") version "2.4.10" // must match your Kotlin version
}

Domain Models

1. Immutable Data Classes

// commonMain/kotlin/com/example/shared/model/User.kt
import kotlin.time.Instant

@Serializable
data class User(
    val id: String,
    val name: String,
    val email: String,
    val avatarUrl: String?,
    val createdAt: Instant,
    val lastActiveAt: Instant?
)

2. Sealed Hierarchies

// commonMain/kotlin/com/example/shared/model/UiState.kt
@Serializable
sealed class UiState<out T> {
    @Serializable
    data object Loading : UiState<Nothing>()

    @Serializable
    data class Success<T>(val data: T) : UiState<T>()

    @Serializable
    data class Error(val message: String, val code: String? = null) : UiState<Nothing>()
}

// Usage with type parameter
@Serializable
sealed class HomeState {
    @Serializable
    data object Loading : HomeState()

    @Serializable
    data class Loaded(val user: User, val items: List<Item>) : HomeState()

    @Serializable
    data class Error(val message: String) : HomeState()
}